Method of upgrading biomass, upgraded biomass,  biomass water slurry and method of producing same, upgraded biomass gas, and method of gasifying biomass

ABSTRACT

This method of upgrading a biomass comprises: an upgrading step for performing upgrading treatment of a cellulose based biomass with an oxygen/carbon atomic ratio of at least 0.5, in presence of water and under a pressure of at least saturated water vapor pressure, and reducing said oxygen/carbon atomic ratio of said biomass to no more than 0.38, and a separation step for separating an upgraded reactant obtained from said upgrading step into a solid component and a liquid component.

TECHNICAL FIELD

The present invention relates to a method of upgrading a cellulose basedbiomass, a method of converting a cellulose based biomass into a slurry,and a method of gasifying upgraded biomass.

BACKGROUND ART

Slurries formed by crushing solid fuels such as coal and then addingwater and additives are known as CWM or CWF (Coal Water Mixture/CoalWater Fuel), and are consequently attracting considerable attention asnew fuels.

From the viewpoint of handling, a slurry fuel requires a viscosity of nomore than 1,500 mPa·s (rotary viscometer, 25° C., shear rate value of100 [1/sec], these settings also apply below). Furthermore, with thedemand in recent years for higher heating values and higher combustionefficiency, heating values of at least 16.5 MJ/kg (4,000 kcal/kg) arerequired.

The increase in carbon dioxide gas emissions as a result of the hugeconsumption of fossil fuels is a significant cause of global warming,and is leading to increased pressure for reductions in carbon dioxidegas emissions. Biomass, including materials such as timber, is anon-fossil based renewable energy considered to produce zero carbondioxide emissions, and because the ash content and the sulfur contentare extremely low, the investment costs for combustion facilities can bereduced.

Timber thinnings, wood scraps from wood processing, prunings fromroadside trees, bagasse, rice straw, and used paper are largely unused,and are either dumped or disposed of for a fee, and if these types ofmaterials could be used as fuels, then it would enable effective use ofunused organic resources. These unused organic resources are solids of avariety of different forms, and if these solids could be liquefied orconverted to a slurry in a similar manner to coal, then a significantexpansion in the range of possible uses could be expected.

With these circumstances in mind, at the 15th International Conferenceon Coal and Slurry Technology in 1990, the Energy and EnvironmentalResearch Center at the University of North Dakota reported thegeneration of a slurry fuel by hot water treatment of timber.

However, the solid fraction concentration of the slurry reported by theUniversity of North Dakota was no more than a maximum of approximately48 mass %, and slurries of higher concentrations could not be produced.At a solid fraction concentration of approximately 48 mass %, theheating value of the slurry is only approximately 3,400 kcal/kg. If anattempt is made to increase the solid fraction concentration in order toincrease the heating value, then the slurry solidifies and cannot behandled as a slurry.

Gasification of these unused organic resources of biomass origin bypartial oxidation reactions, and subsequent use as gas fuels orsynthetic gases for chemical reactions is also being investigated.

In the case of a direct gasification of a biomass, if the reactiontemperature is less than 800° C., then the quantities of tar, soot andchar produced increase, and operation of the gasification furnacebecomes difficult. As a result, the partial oxidation reactiontemperature must be maintained at a high temperature of at least 800° C.In order to maintain the partial oxidation reaction temperature at ahigh temperature of at least 800° C., the quantity of oxygen suppliedmust be increased, and in such cases the usage efficiency of the coolantgas decreases. A further problem arose in that the concentration of H₂and CO, which represent the active ingredients within the targetedproduct gas, also decreases.

Furthermore, in a method in which a raw material biomass is crushed toform chips, because the production of chips smaller than a certain sizeis impossible, performing the gasification reaction within a pressurizedsystem was problematic. In addition, because the biomass cannot bereduced to small enough particles, the rate of the partial oxidationreaction by oxygen is slow.

DISCLOSURE OF INVENTION

The inventors of the present invention discovered that by using acellulose based biomass with an original oxygen/carbon atomic ratio ofat least 0.5 as a raw material, and then upgrading the biomass to reducethis oxygen/carbon atomic ratio to no more than 0.38, a fuel having asuperior quality can be stably produced with a high heating value forthe solid component of the upgraded reactant of at least 25.1 MJ/kg(6,000 kcal/kg).

A method of upgrading a biomass according to the present inventioncomprises an upgrading step for performing upgrading treatment of acellulose based biomass with an oxygen/carbon atomic ratio of at least0.5, in the presence of water and under a pressure of at least thesaturated water vapor pressure, to reduce the oxygen/carbon atomic ratioto no more than 0.38, and a separation step for separating the upgradedreactant obtained from the upgrading step into a solid component and aliquid component. An upgraded biomass of the present invention is abiomass obtained via the above upgrading method.

From an upgraded biomass of the present invention, a biomass waterslurry having a heating value which is adequate as an alternative fuelto heavy oil or coal can be easily produced with a high solid fractionconcentration. The upgraded biomass can be used as a solid fuel in thesame manner as coal without further upgrading process, and can also beused as a soil conditioner or an adsorbent.

A method of producing a biomass water slurry according to the presentinvention comprises an upgrading step for performing upgrading treatmentof a cellulose based biomass raw material in the presence of water undera pressure of at least the saturated water vapor pressure, a separationstep for separating the upgraded reactant obtained from the upgradingstep into a solid component and a liquid component, a crushing step forcrushing the solid component obtained from the separation step to anaverage particle size of no more than 30 μm using a crushing device, anda mixing step for adding additives, and where necessary water, to thesolid component and then mixing. The crushing step and the mixing stepmay be conducted either simultaneously, or sequentially in the orderdescribed above.

According to a method of producing a biomass water slurry of the presentinvention, a slurry with a high solid fraction concentration and aheating value which is adequate as an alternative fuel to heavy oil orcoal, which does not lose slurry characteristics even on long termstorage, and with a viscosity which enables transportation by pipe canbe produced with good stability using a cellulose based biomass, whichconventionally has not been effectively utilized, as the raw material.

A biomass water slurry of the present invention comprises, as a solidfraction, at least 50 mass % of an upgraded biomass, which is producedby upgrading a cellulose based biomass raw material in the presence ofwater and under a pressure of at least the saturated water vaporpressure, and then crushing the product to an average particle size ofno more than 30 μm.

A biomass water slurry of the present invention has a high solidfraction concentration, a heating value which is adequate as analternative fuel to heavy oil or coal, and a viscosity which enablestransportation by pipe. The slurry can be stored with good stability,and even if stored for extended periods, the solid fraction and liquidwithin the slurry will not separate.

A biomass water slurry of the present invention and a method ofproducing such a slurry can utilize, as a raw material, a biomass formedfrom cellulose products which are conventionally ineffectively used,including wood based biomass such as timber thinnings, wood scraps fromwood processing such as sawdust, chips and mills ends, prunings fromroadside trees, wood based waste from construction, bark, anddriftwoods; biomass from grasses such as rice straw, wheat or barleystraw and bagasse; as well as bamboo, bamboo grass, burdock and usedpaper. Accordingly, resources can be utilized more effectively, andnon-fossil based renewable energy considered to produce zero carbondioxide emissions can be obtained, providing an effective countermeasureagainst environmental problems such as increases in carbon dioxide gasemissions. Furthermore, because the ash content and the sulfur contentare extremely low, the investment costs for combustion facilities canalso be reduced.

In a method of gasifying an upgraded biomass of the present invention,an upgraded biomass is subjected to gasification treatment at agasification temperature within a range from 800 to 1300° C. and agasification pressure of 0.1 to 10 MPa, in the presence of a gasifyingagent comprising 25 to 40% of the quantity of oxygen required forcomplete combustion, and a required quantity of steam. An upgradedbiomass gas of the present invention is a gas obtained from the abovegasification method comprising hydrogen and carbon monoxide as primaryconstituents.

The aforementioned gasification treatment refers to gasification bypartial oxidation, which utilizes oxygen and steam as the gasifyingagent, and restricts the quantity of oxygen supplied to approximately ¼to 1/2.5 the quantity required for complete combustion.

According to a gasification method of the present invention, thequantity of oxygen supplied during direct oxidation can be reduced incomparison with the case in which a raw biomass is directly gasified,and the efficiency of the coolant gas can be improved. In addition, theconcentration of H₂ and CO, which represent the active ingredientswithin the gasified product which is generated, can also be increased.

BEST MODE FOR CARRYING OUT THE INVENTION

As follows is a description of preferred embodiments of the presentinvention. However, the present invention is in no way limited to theexamples presented below, and for example, features from the examplesmay also be suitably combined.

Examples of suitable cellulose based biomass raw materials which can beused in the present invention include biomass from cellulose products,including wood based biomass such as timber thinnings, wood scraps fromwood processing such as sawdust, chips and mills ends, prunings fromroadside trees, wood based waste from construction, bark and driftwoods;biomass from grasses such as rice straw, wheat or barley straw andbagasse; as well as bamboo, bamboo grass, burdock and used paper. Inaddition, provided they incorporate sufficient cellulose to enable useas a raw material, sludge, animal dung, agricultural waste and urbanwaste can also be used. Of the above cellulose based biomass materials,wood based biomass is particularly preferred.

Prior to the upgrading process, the cellulose based biomass raw materialis preferably shredded to produce particle fragments of no more than 50mm, and even more preferably no more than 5 mm, and most preferably nomore than 1 mm. When the shredded raw material is supplied into theupgrading process, the shredded raw material may be converted to aslurry in an aqueous medium such as water. However, there is nolimitation in the method of introduction of the shredded raw material.The shredded raw material may be supplied directly into the upgradingprocess without converted into a slurry.

The upgrading step reduces the oxygen content of the cellulose basedbiomass raw material, and improves the heating value of the biomass as afuel, and the upgrading treatment is performed in the presence of water,under a pressure of at least the saturated water vapor pressure, for apredetermined time period, and within a predetermined temperature range.

There are no particular restrictions on the treatment temperature in theupgrading process, although temperatures from 250 to 380° C. arepreferred, and temperatures from 270 to 350° C. are even more desirable.There are no particular restrictions on the treatment pressure, althoughthe pressure is preferably from 0.5 to 5 MPa higher, and even morepreferably from 1 to 3 MPa higher, than the saturated water vaporpressure.

There are no particular restrictions on the treatment time, althoughtime periods from 5 to 120 minutes are preferred, and time periods from10 to 60 minutes are even more desirable. The treatment time relates tothe treatment temperature, and as the treatment temperature increases,the treatment time can be shortened, whereas if the treatmenttemperature is low, then the treatment time should be lengthened.

The upgrading process may utilize a batch treatment using an autoclave,or a continuous reaction apparatus formed from either one, or two ormore reaction zones. During the upgrading process, in order to ensurethe temperature is maintained within the above range, the conditionswithin the apparatus must be maintained using pressurized hot water, anda pressure lowering system for cooling the apparatus and returning thepressure to normal pressure is also required.

The upgraded reactant obtained from the upgrading process is separatedinto a solid component and a liquid component in a separation process.The separation process may include not only the separation of the solidcomponent from the liquid component, but where necessary also a dryingtreatment in those cases in which the water content of the solidcomponent is high. The solid component is dewatered until the solidfraction concentration is at least 50 mass %, and even more preferablyat least 70 mass %. The separated liquid component may be reused as thewater required within the upgrading process.

The separation of the solid component and the liquid component withinthe separation process may utilize any type of apparatus typically usedfor separation, including a leaf filter, a filter press, a presser, acentrifugal filter, or a centrifugal separator. The separation may beperformed at high temperature, provided handling is possible, but mayalso be conducted at room temperature. In those cases in which thedegree of dewatering is insufficient, drying is performed via a heateddrying method until the required solid fraction concentration isobtained.

Following removal of the liquid component in the separation process anddewatering to a predetermined solid fraction concentration, the solidcomponent is then crushed with a crushing device to an average particlesize of no more than 30 μm. Examples of suitable crushing devicesinclude ball mills, rod mills, hammer mills, disc grinding typecrushers, fluid energy mills, or combinations of two or more of theabove devices. The crushing may utilize either dry crushing or wetcrushing, although from the viewpoint of energy efficiency, wet crushingis preferred.

In order to manufacture a biomass water slurry of the present invention,the average particle size of the crushed product obtained from the solidcomponent by the above separation process should be no more than 30 μm,and is preferably no more than 20 μm, and even more preferably no morethan 15 μm, and most preferably no more than 10 μm. The average particlesize refers to values measured using a microtrac (FSA model,manufactured by Nikkiso Co., Ltd.).

In those cases in which a crushed product with an average particlediameter of no more than 30 μm is produced via a one stage crushingtreatment, the crushed product may be sent, as is, to the mixingprocess. In those cases in which one stage crushing does not produce anaverage particle diameter of no more than 30 μm, the crushed product canbe re-crushed to reduce the average particle diameter to a value of nomore than 30 μm. Re-crushing may be performed via a closed system inwhich sieving is conducted at a certain particle size, with undersizeparticles sent directly to the mixing step, and oversize coarseparticles subjected to re-crushing.

Subsequently in the mixing process, additives, and where necessarywater, are added to the crushed solid component, and mixing isperformed, yielding a biomass water slurry. Examples of additivesinclude anionic, cationic and nonionic surfactants, which can be usedsingularly, or in combinations of two or more additives. Appropriateadditives are selected in accordance with the properties of the crushedsolid matter.

Examples of suitable anionic surfactants which can be used include alkylsulfate esters, higher alcohol sulfate esters, nonionic ether sulfateesters, olefin sulfate esters, polyoxyethylene alkyl(alkylphenol)sulfate esters, alkylallyl sulfonates, dibasic ester sulfonates,alkylbenzene sulfonates, alkylnaphthalene sulfonates, dialkylsulfosuccinates, alkyl phosphate esters, and acyl sarcosinates.

Examples of suitable cationic surfactants which can be used includealkyl amines, quaternary amines, and alkylpyridinium sulfates.

Examples of suitable nonionic surfactants which can be used includepolyoxyalkyl ethers, polyoxyethylene alkylphenol ethers, oxyethyleneoxypropylene block polymers, polyoxyethylene alklyamines, sorbitan fattyacid esters, polyoxyethylene sorbitan fatty acid esters,alkyltrimethylammonium chloride, alkyldimethylbenzylammonium chloride,polyoxyethylene fatty acid esters, aliphatic alcohol polyoxyethyleneethers, polyhydric alcohol fatty acid esters, and fatty acidethanolamides.

Amphoteric surfactants such as alkyl betaines can also be used.

The net quantity of additives added is preferably no more than 1.0 mass%, and even more preferably no more than 0.1 mass %, relative to thecrushed solid component. In those cases in which water is added togetherwith the additives, then the additives can be added to the water toproduce a predetermined additives concentration, and this mixture thenmixed with the solid component. Alternatively, the water, the solidcomponent, and the additives can all be combined simultaneously and thenmixed. The mixer can utilize any form of mixer, although a mixer with apowerful mixing action is preferable.

The crushing process and the mixing process may comprise crushing of thesolid fraction in the crushing process, followed by supply of thecrushed solid matter to the mixing process, or alternatively thecrushing process and the mixing process can also be conductedsimultaneously.

For biomass water slurries obtained via the steps described above,because higher solid fraction concentration values produce high heatingvalues, the concentration should be kept as high as possible. Solidfraction concentration values of at least 50 mass % are preferred, withconcentration levels of at least 55 mass % even more preferred, andconcentration levels of at least 60 mass % the most desirable.

On the other hand, in order to enable transportation of a biomass waterslurry by pipe, the biomass water slurry should have a low viscosity ofpreferably no more than 1,500 mPa·s, and even more preferably no morethan 1,000 mPa·s.

During conversion to a water slurry, by using an upgraded crushedbiomass with a higher solid fraction concentration than is desirable fora biomass water slurry, and then mixing this upgraded crushed biomasswhile gradually adding either water containing additives, or additivesand water separately, and then stopping the addition of water at thepoint the viscosity falls rapidly, excessive dilution of the upgradedbiomass with water can be avoided, which is preferable.

A biomass water slurry obtained in the manner described above has a highsolid fraction concentration, and a heating value which is adequate asan alternative fuel to heavy oil or coal, and in addition has aviscosity which makes pipe transportation possible. Furthermore, theslurry can be stored with good stability, and even if stored forextended periods, the solid fraction and the liquid within the slurrywill not separate to a degree likely to cause operational problems.

This biomass water slurry is able to utilize, as a raw material, abiomass formed from cellulose products which are conventionallyineffectively used, including wood based biomass such as timberthinnings, wood scraps from wood processing such as sawdust, chips andmills ends, prunings from roadside trees, wood based waste fromconstruction, bark and driftwoods; biomass from grasses such as ricestraw, wheat or barley straw and bagasse; as well as used paper.Consequently, resources can be utilized more effectively, and becausethe slurry is a non-fossil based renewable energy considered to producezero carbon dioxide emissions, it provides one effective countermeasureagainst environmental problems such as increases in carbon dioxide gasemissions. Furthermore, because the ash content and the sulfur contentof this biomass water slurry are extremely low, the investment costs forcombustion facilities can also be reduced.

A method of upgrading a biomass according to another embodiment of thepresent invention uses biomass raw materials such as those describedabove in which the oxygen/carbon atomic ratio within the raw materialsis at least 0.5 in all cases. Examples include Japanese cedar with anoxygen/carbon atomic ratio of 0.620, pine with a ratio of 0.632, acaciawith a ratio of 0.644, bamboo with a ratio of 0.693, and burdock with aratio of 0.949. These oxygen/carbon atomic ratios are values obtained bymeasurements on dried samples using mass spectrometry, and althoughthere is some variation, most values are substantially constant for eachvariety of plant. In comparison, the equivalent ratio for coal, althoughdependent on the type of coal, is typically from 0.1 to 0.3.

The cellulose based biomass raw material used in the upgrading processis shredded first, in the same manner as described above, and ispreferably reduced to particle fragments of no more than 50 mm, and evenmore preferably no more than 5 mm, and most preferably no more than 1mm.

In this method of upgrading a biomass, the oxygen/carbon atomic ratio ofthe cellulose based biomass raw material is reduced, and the heatingvalue as a fuel is increased. Specifically, by conducting the upgradingtreatment of a cellulose based biomass raw material with anoxygen/carbon atomic ratio of at least 0.5, in the presence of water,under a pressure of at least the saturated water vapor pressure, for apredetermined time period, and within a predetermined temperature range,the oxygen/carbon atomic ratio is reduced to no more than 0.38.

The quantity of water added to the cellulose based biomass raw material,including the existing water content within the cellulose based biomassraw material, is preferably within a range from approximately 1 to 20fold the mass (dry base) of the cellulose based biomass raw material,with quantities from 5 to 15 fold being even more desirable. The watermay utilize recirculated liquid separated from the upgraded reactant inthe separation process described below.

The treatment temperature in the upgrading process is preferably withina range from 250 to 380° C., and even more preferably from 270 to 350°C. The operating pressure is preferably from 0.5 to 5 MPa higher, andeven more preferably from 1 to 3 MPa higher, than the saturated watervapor pressure.

There are no particular restrictions on the treatment time in theupgrading process, although time periods from 5 to 120 minutes arepreferred, and time periods from 10 to 60 minutes are even moredesirable. As the treatment temperature increases, the treatment timecan be shortened, whereas if the treatment temperature is low, then thetreatment time should be lengthened.

The upgrading process may utilize a batch treatment using an autoclave,or a continuous reaction apparatus formed from either one, or two ormore reaction zones. During the upgrading process, in order to ensurethe temperature is maintained within the above range, the conditionswithin the apparatus must be maintained using pressurized hot water, anda pressure lowering system for cooling the apparatus and returning thepressure to normal pressure is also required.

The upgraded reactant obtained from the upgrading process is separatedinto a solid component and a liquid component in a separation process.The separation process of the present invention includes not only theseparation of the solid component from the liquid component, but wherenecessary also a drying treatment using heated drying or the like, whichis performed in those cases in which the water content of the solidcomponent is high.

The solid component produced from the separation process is obtained asan upgraded biomass cake. The solid fraction concentration of this cakeis preferably at least 50 mass %, and even more preferably at least 60mass %. The liquid component separated during the separation process maybe reused as the water required within the upgrading process.

The separation of the solid component and the liquid component withinthe separation process may utilize any type of apparatus typically usedfor separation, including a leaf filter, a filter press, a presser, acentrifugal filter, or a centrifugal separator. The separation may beperformed at high temperature, provided handling is possible, but mayalso be conducted at room temperature.

The conditions within the upgrading process of the present invention,such as the upgrading temperature, pressure, and time period aresuitably selected so as to achieve an upgraded reactant with anoxygen/carbon atomic ratio of no more than 0.38, and preferably no morethan 0.3. Taking into consideration the energy efficiency during theupgrading process, the lower limit for the oxygen/carbon atomic ratio isapproximately 0.1.

Comparing the oxygen/carbon atomic ratio in the biomass with theproduction of charcoal obtained by carbonization of timber, in the caseof charcoal, the timber is baked at 400 to 1000° C. and undergoesthermal decomposition at a high temperature, and the product has acarbon content of greater than 90% and an oxygen content of almost 0,whereas in the present invention, upgrading treatment is performed inthe presence of water, at a lower temperature and a higher pressure thanthat used in the charcoal baking, and a mild thermal decompositionprocess which partially deoxygenates the raw material produces anoxygen/carbon atomic ratio of no more than 0.38.

If the weight of the raw material timber is deemed 100, then therecovered weight in the case of charcoal is approximately 10 to 25%,whereas the recovered weight of upgraded reactant in the presentinvention is at least 40%, meaning the fuel recovery rate is high.

The solid component of the upgraded reactant obtained in the separationprocess following the upgrading treatment to reduce the oxygen/carbonatomic ratio to no more than 0.38 has a heating value per dried weightunit of at least 27 MJ/kg. Even if converted to a water slurry to form aslurry fuel as described below, this type of solid component stillyields a high quality fuel with a heating value per dried weight unit ofat least 16.5 MJ/kg (at least 4,000 kcal/kg). In other words, with thisupgrading method, crushing of the upgraded product is simple, and anupgraded biomass can be produced which displays good affinity for waterand can be converted to a high density water slurry fuel. In addition toslurry fuels, this upgraded biomass may also be combusted directly as asolid component, or can also be used as a high heating value fuel, andmixed with existing fuels such as coal and then combusted within aboiler.

The weight of the volatile component within the upgraded biomass ispreferably at least 50%. The weight of the volatile component refers tothe value measured in accordance with JIS M8812, and is the valueobtained by subtracting the water content from the mass reduction ratioobserved when a sample is heated for 7 minutes at 900° C. without anyair contact. The larger the volatile component, the better thecombustibility will become.

This upgraded biomass can be converted to a low viscosity slurry with ahigh solid fraction concentration, which is capable of pipetransportation, by adding additives, adding further water if necessary,and then crushing and mixing the mixture, for example. The solidfraction concentration is typically at least 50 mass %, and preferablyat least 55 mass %, and even more preferably at least 60 mass %.

Examples of suitable additives include the anionic, cationic andnonionic surfactants described above, which can be used singularly, orin combinations of two or more additives, and can be selected inaccordance with the properties of the crushed solid matter.

In this method, the net quantity of additives added is preferably nomore than 1.0 mass %, and even more preferably no more than 0.1 mass %,relative to the solid component. In those cases in which water is addedtogether with the additives, then in the same manner as described above,a mixture of the additives and water can be mixed with the solidcomponent, or alternatively, the water, the solid component, and theadditives can all be combined simultaneously and then mixed.

In the crushing of the upgraded biomass, crushing is conducted so thatthe average particle size of the upgraded biomass particles ispreferably no more than 30 μm, and even more preferably no more than 20μm, and most preferably no more than 15 μm. The average particle sizerefers to values measured using a microtrac (FSA model, manufactured byNikkiso Co., Ltd.).

Examples of suitable crushing devices that can be used include ballmills, rod mills, hammer mills, disc grinding type crushers, fluidenergy mills, or combinations of two or more of the above devices. Thecrushing may utilize either dry crushing or wet crushing, although fromthe viewpoint of energy efficiency, wet crushing is preferred.

Either one stage or multistage crushing can be used. In the case ofmultistage crushing, a closed system may be used in which the crushedproduct from the first stage is sieved at a certain particle size, andoversize coarse particles are subjected to re-crushing.

Mixing the crushed upgraded biomass enables the production of a biomasswater slurry. The mixer can utilize any form of mixer, although a mixerwith a powerful mixing action is preferable. The crushing process andthe mixing process may comprise crushing of the solid fraction in thecrushing process, followed by supply of the crushed solid matter to themixing process, or alternatively the crushing process and the mixingprocess can also be conducted simultaneously. The slurry may be producedby only one of the crushing process and the mixing process.

During conversion to a biomass water slurry through mixing, by using anupgraded crushed biomass with a higher solid fraction concentration thanis desirable for a biomass water slurry, and then mixing this upgradedcrushed biomass while gradually adding either water containingadditives, or additives and water separately, and then stopping theaddition of water at the point the viscosity falls rapidly, excessivedilution of the upgraded biomass with water can be avoided, which isdesirable.

A biomass water slurry obtained in the manner described above has a highsolid fraction concentration, and a heating value which is adequate asan alternative fuel to heavy oil or coal, and also displays a viscositywhich makes pipe transportation possible.

Because the upgraded biomass is subjected to upgrading treatment at apressure of at least the saturated water vapor pressure, to generate anoxygen/carbon atomic ratio of no more than 0.38, the biomass contains notoxic bacteria, and is also quite porous, and consequently when mixedwith soil, the biomass provides breeding sites for useful soil bacteriaand also adsorbs harmful components within the soil, meaning theupgraded biomass is useful as a soil conditioner, and can also be usedas an adsorbent.

In addition, because this biomass water slurry utilizes, as a rawmaterial, a biomass formed from cellulose products which areconventionally ineffectively used, including wood based biomass such astimber thinnings, wood scraps from wood processing such as sawdust,chips and mills ends, prunings from roadside trees, wood based wastefrom construction, bark and driftwoods; biomass from grasses such asrice straw, wheat or barley straw and bagasse; as well as used paper,resources can be utilized more effectively, and a non-fossil basedrenewable energy considered to produce zero carbon dioxide emissions canbe generated, providing one effective countermeasure againstenvironmental problems such as increases in carbon dioxide gasemissions. Furthermore, because the ash content and the sulfur contentof this biomass water slurry are extremely low, the investment costs forcombustion facilities can also be reduced.

Next is a description of a method of gasifying an upgraded biomass.

In order to gasify an upgraded biomass obtained through the methoddescribed above, oxygen and steam are used as a gasifying agent. Thequantity of oxygen is set at approximately ¼ to 1/2.5 the quantityrequired for complete combustion of the upgraded biomass. The quantityof oxygen required for gasification is related to the gasificationtemperature. Oxygen may be substituted with air. In this method, for apreset gasification temperature, gasification can be achieved with asmaller quantity of oxygen than the case in which a raw biomass isgasified.

There are no particular restrictions on the gasification temperature,provided the temperature is sufficient for gasification to occur, and inorder to suppress the generation of tar and soot, the gasificationtemperature is typically set within a range from 800 to 1300° C., andpreferably from 800 to 1200° C. There are no particular restrictions onthe gasification pressure, and values from 0.1 to 10 MPa can be used.Taking into consideration treatment of the generated gas during laterstages, it is preferable that the gasification is conducted at a highpressure of 0.5 to 10 MPa.

The quantity of steam supplied during the gasification treatment ispreferably determined so that (supplied quantity of oxygen/2+quantity ofoxygen within supplied steam+quantity of oxygen within rawmaterial)/(quantity of carbon within raw material) [mol/mol]=2.0 to 6.0.In addition to oxygen and steam, other gasifying agents such as carbondioxide may also be used where necessary.

The upgraded biomass used in the gasification may be a dried biomass, abiomass containing water, or a slurry produced by adding water. A powderor slurry of an upgraded biomass to which coal powder has been added mayalso be used.

The upgraded biomass is easier to crush than a raw biomass, and can alsobe placed under high pressure and supplied to a gasification reactionvessel, and is consequently a desirable raw material for obtaining ahigh pressure gasification product.

By using an upgraded biomass in the gasification process, the quantityof oxygen supplied can be reduced in comparison with the case in which araw biomass is oxidized directly, and the efficiency of the coolant gascan be improved. In addition, the concentration of H₂ and CO, whichrepresent the active ingredients within the gasified product which isgenerated, can also be improved.

Furthermore, if an upgraded biomass is used, then the reduction of thebiomass to small particles by crushing can be achieved with greaterreliability, direct gasification by a partial oxidation reaction can beperformed efficiently, and the gasification reaction can be conductedeasily at a high pressure.

Furthermore, gasification of biomass comprising wood or the like isusually achievable at low temperatures of approximately 800° C., but tarand carbon deposition cause a reduction in gasification rate, and havebeen reported to cause operational trouble (reference: Biomass Handbook,edited by the Japan Institute of Energy, 2002, p 95). In contrast, in agasification method of the present invention, tar and soot depositiondoes not occur, and the reduction in efficiency and operational troublesdescribed above do not arise.

EXAMPLES Example 1

3,300 g of water was added to 350 g of dried Acacia mangium (timber)which had been shredded to particles of no more than 1 mm, and themixture was then stirred. The thus obtained mixture was placed in a 10liter autoclave, and upgrading treatment was performed by raising thetemperature from room temperature to 330° C. over a 3 hour period, andadjusting the pressure to 15.6 MPa. This state was then maintained for10 minutes, and the mixture was then cooled to 80° C. over a 3 hourperiod, to yield a black colored slurry. This slurry was filtered usinga Nutsche filter, and the thus obtained solid component was dried, andyielded 158 g of a black colored powder.

50 g of this powder was crushed for 30 hours in a 1 liter ball mill, and40 g of a fine powder was recovered. Measurement of the particle sizedistribution of this fine powder using a microtrac (FSA model,manufactured by Nikkiso Co., Ltd.) revealed an average particle size of8.2 μm.

With 40 g of this fine powder being mixed, water containing 2 mass % ofa surfactant (NSF, manufactured by Dai-Ichi Kogyo Seiyaku Co., Ltd.) wasadded gradually, and at the point the slurry viscosity fell rapidly,addition of the water was stopped, thereby yielding a high viscosityslurry. The solid fraction concentration of this slurry was 67 mass %,and the viscosity was 770 mPa·s. This slurry remained in a slurry stateeven after storage for 2 months at room temperature.

When this biomass water slurry was used as the fuel for a combustiontest furnace for observing a droplet combustion process, it was evidentthat the fuel could be used as an adequate alternative fuel to heavyoil. Furthermore, in terms of the facts that the ash content was lessthan 1 mass %, and the sulfur content was essentially non-existent, thebiomass water slurry was superior to heavy oil.

Example 2

With the exceptions of performing the upgrading treatment using 470 g ofAcacia mangium which had been dried and shredded to particles of no morethan 1 mm and 4,300 g of water, and adjusting the set temperature andset pressure for the upgrading treatment to 300° C. and 11 MParespectively, a slurry was obtained in the same manner as the example 1.The average particle size of the fine powder following crushing with theball mill was 10.3 μm.

The solid fraction concentration of the slurry obtained after mixing was66 mass %, and the slurry viscosity was 830 mPa·s. This slurry remainedin a slurry state even after storage for 2 months at room temperature.The characteristics of this slurry as a fuel were the same as those ofthe biomass water slurry of the example 1.

Example 3

With the exceptions of performing the upgrading treatment using 290 g ofAcacia mangium which had been dried and shredded to particles of no morethan 1 mm and 2,700 g of water, and adjusting the set temperature andset pressure for the upgrading treatment to 350° C. and 18.8 MParespectively, a slurry was obtained in the same manner as the example 1.The average particle size of the fine powder following crushing with theball mill was 9.5 μm.

The solid fraction concentration of the slurry obtained after mixing was68.5 mass %, and the slurry viscosity was 990 mPa·s. This slurryremained in a slurry state even after storage for 2 months at roomtemperature.

Example 4

With the exceptions of performing the upgrading treatment using 430 g ofJapanese cedar which had been dried and shredded to particles of no morethan 1 mm and 3,600 g of water, and adjusting the set temperature andset pressure for the upgrading treatment to 270° C. and 14 MParespectively, a slurry was obtained in the same manner as the example 1.The average particle size of the fine powder following crushing with theball mill was 11.3 μm.

The solid fraction concentration of the slurry obtained after mixing was67 mass %, and the slurry viscosity was 770 mPa·s. This slurry remainedin a slurry state even after storage for 2 months at room temperature.The characteristics of this slurry as a fuel were the same as those ofthe biomass water slurry of the example 1.

Example 5

With the exceptions of performing the upgrading treatment using 460 g ofAcacia mangium which had been dried and shredded to particles of no morethan 1 mm, using 3,200 g of the liquid obtained by filtering theupgrading treatment slurries obtained in the example 2 and the example 3instead of water, and adjusting the set temperature and set pressure forthe upgrading treatment to 330° C. and 18 MPa respectively, a slurry wasobtained in the same manner as the example 1. The average particle sizeof the fine powder following crushing with the ball mill was 11 μm.

The solid fraction concentration of the slurry obtained after mixing was70 mass %, and the slurry viscosity was 1,100 mPa·s. This slurryremained in a slurry state even after storage for 2 months at roomtemperature.

Example 6

The upgrading treatment was performed using 470 g of dried Acaciamangium which had been shredded to particles of no more than 1 mm and4,300 g of water, and with the set temperature and set pressure for theupgrading treatment set to 300° C. and 11 MPa respectively. Furthermore,with the exception of altering the time for which the set temperaturewas maintained to 60 minutes, a slurry was obtained in the same manneras the example 1. The upgrading treatment yielded 223 g of a blackcolored powder. The average particle size of the fine powder followingcrushing with a ball mill was 9.9 μm.

The solid fraction concentration of the slurry obtained after mixing was70 mass %, and the slurry viscosity was 940 mPa·s. This slurry remainedin a slurry state even after storage for 2 months at room temperature.

Comparative Example 1, Examples 7 to 9

With the exceptions of performing the upgrading treatment using 470 g ofAcacia mangium which had been dried and shredded to particles of no morethan 1 mm and 4,300 g of water, and adjusting the set temperature andset pressure for the upgrading treatment to 300° C. and 11 MParespectively in the same manner as the example 2, a black colored powderwas obtained in the same manner as the example 1. This was crushedfinely with a ball mill, yielding separate 50 g samples of finelycrushed powder after 4 hours (comparative example 1), after 8 hours(example 7), after 16 hours (example 8) and after 32 hours (example 9)respectively. The average particle sizes of each powder sample were35.2, 25.6, 15.1 and 10.3 μm respectively.

The solid fraction concentrations of each sample when converted to aslurry under the same conditions were 47, 55, 60 and 66 mass %respectively, and in the slurry produced after 4 hours of crushing(comparative example 1), the solid settled out after a few days and theslurry state was lost. The other slurries (example 7 through example 9)all remained in a slurry state even after storage for 2 months at roomtemperature.

Example 10

9,000 g of water was added to 1,000 g of dried Japanese cedar timberwhich had been shredded to particles of no more than 1 mm, and thepressure of the stirred slurry was raised to 15 MPa using a pump. Theslurry was then fed into an electrically heated reaction apparatus witha preheating section of internal diameter 8 mm, an upgrading section,and a cooling section, and was upgraded in the upgrading section at atemperature of 300° C. and with a residence time of 30 minutes. Then itwas cooled to 90° C. by the cooling section, and was left to stand atnormal pressure. The thus obtained slurry was filtered using a Nutschefilter, and the solid component was then dried, and yielded 420 g of ablack colored powder. Drying treatment was conducted for 10 hours at105° C., and the water content within the treated product was reduced tono more than 2 mass %.

Determination of the elemental composition of the dried powder using aCHN coder manufactured by Yanaco Corporation, revealed an oxygen/carbonatomic ratio of 0.258, and furthermore the high heating value (theheating value during combustion, including the heat of condensation ofgenerated H₂O) was 29.9 MJ/kg (7,150 kcal/kg), and the volatilecomponent was 60%. The oxygen/carbon atomic ratio of the raw materialJapanese cedar was 0.620, the high heating value was 0.20.0 MJ/kg (4,780kcal/kg); and the volatile component was 85%.

50 g of the black colored powder was crushed for 30 hours in a 1 literball mill, and 40 g of a fine powder was recovered. Measurement of theparticle size distribution of this fine powder using a microtrac (FSAmodel, manufactured by Nikkiso Co., Ltd.) revealed an average particlesize of 8.2 μm.

With 40 g of this fine powder being mixed, water containing 2 mass % ofa surfactant (NSF, manufactured by Dai-Ichi Kogyo Seiyaku Co., Ltd.) wasadded gradually, and at the point the slurry viscosity fell rapidly,addition of the water was stopped, thereby yielding a high viscosityslurry. The solid fraction concentration of this slurry was 67 mass %,and the viscosity was 770 mPa·s.

When this biomass water slurry was used as the fuel for a combustiontest furnace for observing a droplet combustion process, it was evidentthat the fuel could be used as an adequate alternative fuel to heavyoil. Furthermore, in terms of the facts that the ash content was lessthan 1 mass %, and the sulfur content was essentially non-existent, thebiomass water slurry was superior to heavy oil.

Example 11

Using the same raw material and apparatus as the example 10, but withthe exceptions of setting the raised pressure applied by the pump to 9MPa, and setting the temperature of the upgrading section to 270° C.,the raw material was upgraded, filtered and dried in the same manner asthe example 10, and yielded a black colored powder. The oxygen/carbonatomic ratio of the thus obtained black colored powder was 0.262, thehigh heating value was 29.8 MJ/kg (7,120 kcal/kg), and the volatilecomponent was 60%.

Example 12

Using the same raw material and apparatus as the example 10, but withthe exceptions of setting the raised pressure applied by the pump to 7MPa, and setting the temperature of the upgrading section to 250° C.,the raw material was upgraded, filtered and dried in the same manner asthe example 10, and yielded a black colored powder. The oxygen/carbonatomic ratio of the thus obtained black colored powder was 0.376, thehigh heating value was 27.0 MJ/kg (6,450 kcal/kg), and the volatilecomponent was 68%.

Example 13

Using the same raw material and apparatus as the example 10, but withthe exception of setting the residence time within the upgrading sectionto 5 minutes, the raw material was upgraded, filtered and dried in thesame manner as the example 10, and yielded a black colored powder. Theoxygen/carbon atomic ratio of the thus obtained black colored powder was0.260, the high heating value was 29.7 MJ/kg (7,100 kcal/kg), and thevolatile component was 74%.

Example 14

With the exception of replacing the Japanese cedar raw material withAcacia mangium (oxygen/carbon atomic ratio: 0.644, high heating value:21.0 MJ/kg (5,020 kcal/kg), volatile component: 84%) which had beendried and shredded in the same manner, a black colored powder wasobtained in the same manner as the example 10. The oxygen/carbon atomicratio of the thus obtained black colored powder was 0.243, the highheating value was 30.0 MJ/kg (7,170 kcal/kg), and the volatile componentwas 60%.

Example 15

With the exceptions of replacing the Japanese cedar raw material withpine (oxygen/carbon atomic ratio: 0.632, high heating value: 21.0 MJ/kg(5,010 kcal/kg), volatile component: 84%) which had been dried andshredded in the same manner, setting the raised pressure applied by thepump to 10 MPa, and setting the temperature of the upgrading section to270° C., a black colored powder was obtained in the same manner as theexample 10. The oxygen/carbon atomic ratio of the thus obtained blackcolored powder was 0.230, the high heating value was 30.6 MJ/kg (7,300kcal/kg), and the volatile component was 62%.

Example 16

With the exception of replacing the Japanese cedar raw material withbamboo (oxygen/carbon atomic ratio: 0.632, high heating value: 22.0MJ/kg (5,250 kcal/kg), volatile component: 83%) which had been dried andshredded in the same manner, a black colored powder was obtained in thesame manner as the example 10. The oxygen/carbon atomic ratio of thethus obtained black colored powder was 0.216, the high heating value was30.9 MJ/kg (7,380 kcal/kg), and the volatile component was 61%.

Example 17

With the exception of replacing the Japanese cedar raw material withburdock (oxygen/carbon atomic ratio: 0.949, high heating value: 19.9MJ/kg (4,760 kcal/kg), volatile component: 86%) which had been dried andshredded in the same manner, a black colored powder was obtained in thesame manner as the example 10. The oxygen/carbon atomic ratio of thethus obtained black colored powder was 0.268, the high heating value was29.6 MJ/kg (7,070 kcal/kg), and the volatile component was 59%.

Comparative Example 2

Using the same raw material and apparatus as the example 10, but withthe exceptions of setting the raised pressure applied by the pump to 5MPa, and setting the temperature of the upgrading section to 230° C.,the raw material was upgraded, filtered and dried in the same manner asthe example 10, and yielded a dark brown colored powder. Theoxygen/carbon atomic ratio of the thus obtained powder was 0.496, thehigh heating value was 23.9 MJ/kg (5,700 kcal/kg), and the volatilecomponent was 74%.

Comparative Example 3

Using the same raw material and apparatus as the example 10, but withthe exceptions of setting the raised pressure applied by the pump to 3MPa, and setting the temperature of the upgrading section to 200° C.,the raw material was upgraded, filtered and dried in the same manner asthe example 10, and yielded a brown colored powder. The oxygen/carbonatomic ratio of the thus obtained brown colored powder was 0.615, thehigh heating value was 20.1 MJ/kg (4,800 kcal/kg), and the volatilecomponent was 84%.

Example 18

For a gasification reaction using oxygen blowing, in which the driedblack colored powder obtained through the upgrading treatment of theexample 10 (oxygen/carbon atomic ratio: 0.258, high heating value: 29.9MJ/kg) was supplied at a rate of 1,466 kg/hr, the quantity of oxygenrequired to ensure a gasification reaction vessel temperature of 1,100°C., and the composition of the gas at that time, were determined bysimulation calculations.

Steam was supplied so that (supplied quantity of oxygen/2+suppliedquantity of steam+quantity of oxygen within raw material)/(quantity ofcarbon within raw material)=4.0 [mol/mol]. The results are shown inTable 1.

The quantity of oxygen required was 28.1 kg-mol/hr, the quantity of(CO+H₂) within the product gas was 130.2 kg-mol/hr, and the (CO+H₂) gasconcentration referenced to the dry gas was 84.1%. Furthermore, the coolgas efficiency was 84.9%.

These simulation results are determined based on the product gascomposition reaching a thermodynamic equilibrium within the reversiblereaction equations of equation (1) and equation (2) shown below.

CH₄+H₂O←→CO+3H₂  (1)

CO+H₂O←→CO₂+H₂  (2)

When an apparatus was assembled, and an actual test was performed, theresults obtained were substantially the same as those of the simulationcalculations. Because the gasification was conducted at approximately1100° C., the production of carbon and tar is limited, and consequentlythese factors were ignored in the calculations.

Comparative Example 4

For a gasification reaction using oxygen blowing, in which driedJapanese cedar (oxygen/carbon atomic ratio: 0.620, high heating value:20.0 MJ/kg) was supplied at a rate of 2,340 kg/hr, the quantity ofoxygen required to ensure a gasification reaction vessel temperature of1,100° C., and the composition of the gas at that time, were determinedby simulation calculations.

Steam was supplied so that (supplied quantity of oxygen/2+suppliedquantity of steam+quantity of oxygen within raw material)/(quantity ofcarbon within raw material)=4.0 [mol/mol]. The reason that the rawmaterial quantity was set at 2,340 kg/hr was to ensure that thequantities of (CO+H₂) generated, which represent the active ingredientswithin the product gas, were the same as in the example 18. The resultsare shown in Table 1. The quantity of oxygen required was 39.7kg-mol/hr, the quantity of (CO+H₂) within the product gas was 130.2kg-mol/hr, the same as the example 18, but the (CO+H₂) gas concentrationreferenced to the dry gas was 77.8%. Furthermore, the cool gasefficiency was lower, at 79.3%.

TABLE 1 Example 18 Comparative Example 4 Raw material Dried upgradedmaterial Dried Japanese cedar Setting of Conditions C = 100 kgmolQuantity of (CO + H₂) generated (atomic mol) set as for the example 18,quantity of O₂ for 1100° C. then calculated Raw material supply rate[kg/hr] 1466 2348 Raw material heating value HHV 7150 4730 [kcal/kg]Oxygen supply rate [kg-mol/hr] 28.1 39.7 Ratio relative to oxygenquantity required 26.5 29.1 for complete combustion [%] Steam supplyrate [kg-mol/hr] 89.6 79.1 Gasification pressure [MPa] 70 70Gasification temperature (calculated) [° C.] 1105 1102 Product gasquantities [kg-mol/hr] CO 60.9 62.9 H₂ 69.3 67.3 CO₂ 24.0 36.7 H₂O 58.984.4 CH₄ 0.7 0.4 Cool gas efficiency *) [%] 84.9 79.3 *) Cool gasefficiency = HHV of combustible gas within product gas/HHV of gasifiedraw material, HHV: high heating value

In an oxygen blowing gasification method, the quantity of oxygen usedhas a large effect on the economic viability, and from a comparison ofthe example 18 and the comparative example 4, it is evident that usingthe upgraded material as a raw material enables a reduction in theoxygen supply rate and an improvement in the cool gas efficiency overthe case using a raw biomass. Furthermore, the concentration of theactive ingredients within the product gas can also be improved.

INDUSTRIAL APPLICABILITY

According to the present invention, a slurry with a high solid fractionconcentration and a heating value which is adequate as an alternativefuel to heavy oil or coal, which does not lose slurry characteristicseven on long term storage, and with a viscosity which enablestransportation by pipe, can be produced with good stability using acellulose based biomass, which conventionally has not been effectivelyutilized, as the raw material.

1-8. (canceled)
 9. A method of producing a biomass water slurry,comprising: an upgrading step for performing upgrading treatment of acellulose based biomass raw material in presence of water and under apressure of at least saturated water vapor pressure, a separation stepfor separating an upgraded reactant obtained from said upgrading stepinto a solid component and a liquid component, a crushing step forcrushing said solid component obtained from said separation step to anaverage particle size of no more than 30 μm using a crushing device, anda mixing step for adding additives, and where necessary water, to saidsolid component, and mixing, wherein said crushing step and said mixingstep are performed either simultaneously or sequentially in this order.10. A method of producing a biomass water slurry according to claim 9,wherein said cellulose based biomass is a wood based biomass.
 11. Amethod of producing a biomass water slurry according to claim 9, whereinan average particle size of a solid component crushed in said crushingstep is no more than 20 μm.
 12. A method of producing a biomass waterslurry according to claim 9, wherein said upgrading treatment isconducted at a temperature of 250 to 380° C., for a period of 5 to 120minutes.
 13. A method of producing a biomass water slurry according toclaim 9, wherein a solid fraction concentration of a biomass waterslurry obtained from said mixing step is at least 50 mass %.
 14. Amethod of producing a biomass water slurry according to claim 9, whereina cellulose based biomass raw material used in said upgrading step hasalready undergone shredding.
 15. A method of producing a biomass waterslurry according to claim 14, wherein said shredded cellulose basedbiomass raw material is used in said upgrading step in a water slurryform.
 16. A biomass water slurry comprising, as a solid fraction, atleast 50 mass % of an upgraded biomass produced by upgrading a cellulosebased biomass in presence of water and under a pressure of at leastsaturated water vapor pressure, and crushing to an average particle sizeof no more than 30 μm.
 17. A biomass water slurry according to claim 16,wherein a solid fraction concentration is from 55 to 75 mass %.
 18. Abiomass water slurry according to claim 16, wherein an average particlesize of a solid component is no more than 20 μm. 19-20. (canceled)